MIL-HDBK-1004/10
where
I
=
0.84 A
R
=
38.94 ohms
E
=
0.84 x 38.94
E
=
32.7 V
(2) To allow for rectifier aging and film formation, it is
considered good practice to use a 1.5 multiplying factor.
E = 1.5 x 32.7 = 49.1 V
(3) The nearest commercially available rectifier size meeting
the above requirements is a 60-V, 4-amp, single-phase unit.
h) Rectifier location.
Locate the rectifier adjacent to tank for
the following reasons:
(1)
Usually cheaper to install.
(2)
Easier to maintain.
(3)
Keeps dc voltage drop to a minimum.
i)
dc circuit conductors:
(1)
External to tank: Use No. 2 AWG, HMWPE.
(2)
Interior of tank: Use No. 8 AWG, HMWPE.
No stressing or bending of the cable should be permitted.
Underground Steel Storage Tank. Galvanic cathodic protection is
9.7
designed for an underground steel storage tank as shown in Figure 110. The
tank is already installed and current requirement tests have been made.
9.7.1
Design Data
a)
Tank diameter, 12 feet.
b)
Tank length, 40 feet.
c)
Design for 80 percent coating efficiency, based on experience.
d)
Design for 15-year life.
e)
Current requirements, 0.7 A.
f)
Packaged, 17-pound standard magnesium anodes must be used.
g)
The tank is adequately insulated from foreign structures.
190
Previous Page
